Adjustable-spring attenuator for radiated beams

ABSTRACT

A variable attenuator for use in a radiation beam path comprising at least one obturating element which element is capable of varying its physical form, whereby according to the degree of such variation the element may of itself, or in combination with other elements, attenuate a radiation beam path in which it is placed to a greater or lesser degree, there being further provided control means for providing gradual variation in the physical form of the element.

United States Patent [1 1 McGee ADJUSTABLE-SPRING ATTENUATOR FORRADIATED BEAMS [75] Inventor: KevinMcGee,Newcastle-upon- Tyne, England[73] Assignee: Sir Howard Grubb Parsons 8L Co..

Limited, Newcastle-upon-Tyne, England [22] Filed: Feb. 13, 1974 [21]Appl. No.: 441,991

[30] Foreign Application Priority Data Feb. 13, I973 United Kingdom6961/73 [52] US. Cl. 350/266; 350/270; 350/27l [51] Int. Cl. G02f 1/28[58] Field of Search 350/266, 267, 269, 270,

350/27l; 356/225; 313/l l7; 250/229 [56] References Cited UNlTED STATESPATENTS 3,447,862 6/l969 Elpern 350/266 June 17, 1975 3.610.740 l0/l97l3.756700 9/l973 Aparicin 350/278 Saxe 350/267 Primary Examiner-VincentP. McGraw Attorney, Agent, or Firm--Holman & Stern 5 7 1 ABSTRACT Avariable attenuator for use in a radiation beam path comprising at leastone obturating element which element is capable of varying its physicalform, whereby according to the degree of such variation the element mayof itself, or in combination with other elements, attenuate a radiationbeam path in which it is placed to a greater or lesser degree, therebeing further provided control means for providing gradual variation inthe physical form of the element.

4 Claims, 3 Drawing Figures ADJUSTABLE-SPRING ATTENUATOR FOR RADIATEI)BEAMS FIELD OF THE INVENTION This invention relates to attenuators forradiation beams such as optical beams.

BACKGROUND OF THE INVENTION Many optical instruments require attenuatingdet ices capable of giving precise control ofvarying attenuation of anoptical beam path. Attenuators for instruments such as gas analysers.for example. have generally involved the use of wedge combs or shuttersplaced in the optical beam. calling for carriages and guidesmanufactured to a high degree of accuracy. Previously known precisionattenuators have. therefore, tended to be costly and somewhat complex.

SUMMARY OF THE INVENTION The object of the present invention is toprovide a variable attenuator for the purpose described which. whilstcapable of precise adjustment. is both of simple construction andinexpensive.

According to the present invention a variable attenuator for use in aradiation beam path comprises at least one obturating element whichelement is capable of varying its physical form, whereby according tothe degree of such variation the element may of itself, or incombination with other elements, attenuate a radiation beam path inwhich it is placed to a greater or lesser degree. there being furtherprovided control means for producing gradual variation in the physicalform ofthe element.

In the preferred form of the invention, a variable attenuator includes ahelical coil spring which is placed in the beam path to be attenuated,the coil density of the spring in the beam path being controllable bymeans of a spring take-up arrangement which may be automatically orhand-operated. The spring is prefera bly placed across the full heightor full width of the beam to be attenuated and variation of the springcoil density alters the number of turns met by the beam thus alteringthe degree of obscuration.

The spring may be a compression spring but is preferably an extensionspring continuously under tension for all settings of the attenuator. Itis also possible. however, to use a coil spring varying betweencompression and extension over the operating range of the attenuator.

One embodiment of the invention will now be de scribed with reference tothe accompanying drawing in which:

DESCRIPTION OF THE DRAWING FIG. 1 shows a simple perspective view of anoptical beam path attenuator according to the present inven tion.

FIG. 2 shows a sectional front elevation of a spring take-up arrangementof the attenuator shown in FIG. 1, and

FIG. 3 shows a side elevation of the spring take-up arrangement shown inFIGS. I and 2.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing. theattenuator shown comprises a spring wire coil 1 supported by a bracket 2such that several of the spring coils may interrupt a light beamindicated by arrow A.

I'he coil I is fixed at its lower end to bracket 2 by screws 3. theupper end of the coil being arranged to wind onto the cylinder 4 of acoil take-up arrangement. The latter arrangement comprises. in additionto cylinder 4,11 knurled operating knob S, a shaft 6 and a transversepin 7, in fixed relationship to one another and arranged to rotatetogether by means of the shaft 6 being mounted in a hole in an end wallat the top of cylinder 4. The extreme upper end of the coil is fixedbetween the cylinder 4 and the bracket 2, cylinder 4 being rigidly heldby the bracket.

The arrangement shown enables the number of turns of coil 1 passingthrough a fixed beam area. or path. to be varied by turning the knob 5and thus taking up a greater or lesser number of the coil turns on tocylinder 4.

Typical dimensions for the attenuator shown are as follows:

25 X 40 mm rectangle.

Beam palch' si/e:

S i r approxlniately.

12 thousandths of an inch.

The attenuator described. in addition to being generally mechanicallysimple and robust. is particularly suitable for use in locations subjectto vibration since. al though the coil may vibrate in suchcircumstances. the overall attenuating effect of the coil remainsconstant to a surprisingly high degree.

The invention is not limited to the use of coil springs as attenuatingelements. Alternative forms may comprise, for example, a plurality ofelements of leaf-spring shape, or a deformable strip of zig-zagconfiguration. A further possible embodiment may employ a body ofmaterial capable of transmitting radiation. the change in form of thebody being arranged to alter the path length of radiation through thebody, and thus vary the attenuation of the beam.

It will be appreciated that the invention is not limited to attenuatorsfor optical beams but may also be applied to attenuators for alternativeforms of radiation. for example. infra-red radiation.

I claim:

I. A variable attenuator for use in a radiated beam path comprising atleast one obturating element which element is capable of varying itsphysical form. whereby according to the degree of such variation theelement may of itself, or in combination with other ele ments, attenuatea radiated beam path in which it is placed to a greater or lesserdegree; and control means operatively connected to said obturatingelement for providing gradual variation in the physical form of theelement, said obturating element comprising an elongated. cylindricalhelical coil spring for location with the longitudinal axis of the coilspring normal to the beam path being attenuated. the coil density of thespring in the beam path being substantially infinitely controllablewithin the physical distortion limits of the 3 cylindrical, helical coilspring, the spring defining a cyl inder in elevation for dispositionacross the full height or width of the beam to be attenuated andvariations of the spring coil density causing an alteration in thenumber of turns of the spring met by the beam and thus altering thedegree of the obscuration. said coil spring heing fixedly anchored atone end. and said control means comprising a cylinder element connectedaxially to the other end ofthe coil spring. said coil spring beingcontinuously under stress. and means for adjustahly rotating thecylinder to impose torque on the individual helical coils of the springfor altering the diameter of the cylindrical coil and the spacingbetween adjacent helical coils of the springv 2. A variable attenuatorfor use in combination with a radiated beam for adjustahly-attenuatingthe beam path in relation to the physical extension or detention of anohturating element comprising:

support means having spaced portions defining the general area for whicha radiated beam to be attenuated will pass; at least one. elongated,axially-deformable ohturating element anchored between said supportportions in intercepting relation to said area through which the beamwill pass; and means for adjusting the axial length of said obturatingelement axially between said spaced support portions. said obturatingelement comprising a cylindrical, helical coil spring continuouslystressed be tween said space support portions during all positions ofadjustment.

3. The variable attenuator as claimed in claim 2 in which saidcylindrical. helical coil spring is terminally anchored at one end onone support portion, said other support portion including a cylindricaldrum telescopically and fixedly connected to the other end of saidhelical coil spring whereby axial extension and detention of said coilspring uniformly changes the shape of each of the helical coils and thediameter of the cylindrical coil as well as the distance betweenadjacent helical coils of the spring.

4. The variable attenuator as claimed in claim 3 in which saidcylindrical drum is journaled in said other support portion and isrotatably adjustahly mounted thereon, means for rotating the cylindricaldrum and the cylindrical coil spring for imposing torque along thelongitudinal axis of the cylindrical coil spring and adjustahly windingthe helical coils of the coil spring into an adjusted obturatingrelationship normal to the path of the radiated beam being attenuated.

1. A variable attenuator for use in a radiated beam path comprising atleast one obturating element which element is capable of varying itsphysical form, whereby according to the degree of such variation theelement may of itself, or in combination with other elements, attenuatea radiated beam path in which it is placed to a greater or lesserdegree; and control means operatively connected to said obturatingelement for providing gradual variation in the physical form of theelement, said obturating element comprising an elongated, cylindricalhelical coil spring for location with the longitudinal axis of the coilspring normal to the beam path being attenuated, the coil density of thespring in the beam path being substantially infinitely controllablewithin the physical distortion limits of the cylindrical, helical coilspring, the spring defining a cylinder in elevation for dispositionacross the full height or width of the beam to be attenuated andvariations of the spring coil density causing an alteration in thenumber of turns of the spring met by the beam and thus altering thedegree of the obscuration, said coil spring being fixedly anchored atone end, and said control means comprising a cylinder element connectedaxially to the other end of the coil spring, said coil spring beingcontinuously under stress, and means for adjustably rotating thecylinder to impose torque on the individual helical coils of the springfor altering the diameter of the cylindrical coil and the spacingbetween adjacent helical coils of the spring.
 2. A variable attenuatorfor use in combination with a radiated beam for adjustably-attenuatingthe beam path in relation to the physical extension or detention of anobturating element comprising: support means having spaced portionsdefining the general area for which a radiated beam to be attenuatedwill pass; at least one, elongated, axially-deformable obturatingelement anchored betWeen said support portions in intercepting relationto said area through which the beam will pass; and means for adjustingthe axial length of said obturating element axially between said spacedsupport portions, said obturating element comprising a cylindrical,helical coil spring continuously stressed between said space supportportions during all positions of adjustment.
 3. The variable attenuatoras claimed in claim 2 in which said cylindrical, helical coil spring isterminally anchored at one end on one support portion, said othersupport portion including a cylindrical drum telescopically and fixedlyconnected to the other end of said helical coil spring whereby axialextension and detention of said coil spring uniformly changes the shapeof each of the helical coils and the diameter of the cylindrical coil aswell as the distance between adjacent helical coils of the spring. 4.The variable attenuator as claimed in claim 3 in which said cylindricaldrum is journaled in said other support portion and is rotatablyadjustably mounted thereon, means for rotating the cylindrical drum andthe cylindrical coil spring for imposing torque along the longitudinalaxis of the cylindrical coil spring and adjustably winding the helicalcoils of the coil spring into an adjusted obturating relationship normalto the path of the radiated beam being attenuated.